Vehicle-mounted terminal MCU reset management circuit

Abstract

The invention discloses a vehicle-mounted terminal MCU reset management circuit. The circuit comprises a watchdog circuit; the power-on reset closing circuit is respectively connected with a reset pin of the watchdog chip and the MCU; when the storage battery is powered on, the delay switch controls the first switch tube connected with the reset pin to be cut off, and one end, connected with the MCU, of the first switch tube is in a high-resistance state; after a certain period of time, the time delay switch controls the first switch tube to be switched on, and a reset pin of the watchdog chip is electrically connected with the MCU; the low-voltage detection circuit is respectively connected with a power supply monitoring input pin and a power supply monitoring output pin of the watchdog chip; the power supply monitoring input pin is connected with a storage battery power supply, the power supply monitoring output pin is connected to the MCU, and when the MCU detects that the power supply monitoring output pin outputs a low level, a sleep mode is entered; and the ACC detection circuit is connected with a dog feeding signal input pin of the watchdog chip, and can close a watchdog when the ACC is OFF, so that the MCU in the dormant state is prevented from being reset by the watchdog. The method can adapt to the complex application environment of the vehicle, and the reliable operation of the vehicle-mounted terminal is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle MCU reset, and in particular to a vehicle terminal MCU reset management circuit. Background Art

[0002] In-vehicle OTA devices need to consider the multi-environmental applications on the vehicle. For example, when an abnormal situation occurs that causes the MCU to malfunction, the vehicle terminal needs to be able to quickly resume normal use (for example, the vehicle terminal needs to complete CAN bus communication within 250ms, so the MCU needs to be started immediately) to ensure the smooth operation of the vehicle. In traditional MCU applications, a single watchdog circuit or an internal watchdog circuit of the MCU is mainly used to manage the MCU reset. Due to the complex application environment of automotive electronic equipment and the high requirements for MCU operation reliability, the traditional single watchdog circuit is prone to conflicts or abnormalities when there is a need for sleep. For example, when the battery is powered on, the MCU cannot be fed during flashing, resulting in continuous reset and causing MCU flashing abnormalities; when the battery is abnormally powered off, the MCU sleeps abnormally, etc. Summary of the Invention

[0003] The main purpose of the present invention is to overcome the above-mentioned defects in the prior art and to propose an on-board terminal MCU reset management circuit that can adapt to the complex application environment of the vehicle and ensure the reliable operation of the on-board terminal.

[0004] The present invention adopts the following technical solutions:

[0005] A vehicle terminal MCU reset management circuit, comprising:

[0006] A watchdog circuit, including a watchdog chip;

[0007] The power-on reset shutdown circuit is connected to the reset pin of the watchdog chip and the MCU respectively, and includes a delay switch and a first switch tube. When the battery is powered on, the delay switch controls the first switch tube connected to the reset pin to be turned off, and the end of the first switch tube connected to the MCU is in a high-impedance state. After a certain period of time, the delay switch controls the first switch tube to be turned on, and the reset pin of the watchdog chip is electrically connected to the MCU.

[0008] The low-voltage detection circuit is connected to the power monitoring input pin and the power monitoring output pin of the watchdog chip respectively; the power monitoring input pin is connected to the battery power supply, and the power monitoring output pin is connected to the MCU. When the MCU detects that the power monitoring output pin outputs a low level, it enters sleep mode;

[0009] The ACC detection circuit is connected to the watchdog chip's feeding signal input pin. When ACC is OFF, the watchdog can be turned off to prevent the MCU in sleep state from being reset by the watchdog.

[0010] Preferably, the delay switch includes a first resistor and a first capacitor; one end of the first resistor is connected to the MCU power supply, the other end of the first resistor is connected to one end of the first capacitor and the control end of the first switch tube, and the other end of the first capacitor is grounded; the input end of the first switch tube is connected to the reset pin of the watchdog chip, and the output end of the first switch tube is connected to the MCU.

[0011] Preferably, the power-on reset shutdown circuit also includes a first diode; the first diode is connected in parallel with the first resistor, and the anode of the first diode is connected to the first capacitor, and the cathode of the first diode is connected to the MCU power supply.

[0012] Preferably, the first switching tube is a triode; the control end of the first switching tube is the base, the input end of the first switching tube is the emitter, and the output end of the first switching tube is the collector.

[0013] Preferably, the low-voltage detection circuit includes a fifth resistor, a sixth resistor and an eighth resistor; the battery power supply is connected to the power monitoring input pin through the fifth resistor; the battery power supply is connected to the power monitoring output pin and the MCU respectively through the fifth resistor and the sixth resistor connected in series; one end of the eighth resistor is connected between the fifth resistor and the sixth resistor, and the other end of the eighth resistor is grounded.

[0014] Preferably, the low-voltage detection circuit also includes a seventh resistor and a second switch tube; the control end of the second switch tube is connected to the power detection adapter enable end to detect battery power supplies of different voltage systems, and the output end of the second switch tube is connected between the fifth resistor and the sixth resistor through the seventh resistor.

[0015] Preferably, the low voltage detection circuit further includes a second voltage regulator tube; the second voltage regulator tube is connected in parallel with the eighth resistor, and the cathode of the second voltage regulator tube is connected between the fifth resistor and the sixth resistor, and the anode of the second voltage regulator tube is grounded.

[0016] Preferably, the second switching tube is a triode; the control end of the second switching tube is the base, and the output end of the second switching tube is the collector.

[0017] Preferably, the ACC detection circuit includes a third switch tube; the control end of the third switch tube is connected to the battery ignition signal, and the output end of the third switch tube is connected between the MCU power supply and the dog feeding signal input pin of the watchdog chip; the dog feeding signal input pin is also connected to the MCU.

[0018] Preferably, the third switching tube is a triode; the control end of the third switching tube is the base, and the output end of the third switching tube is the collector.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention focuses on various abnormal situations that may cause vehicle-mounted terminal abnormalities and abnormal situations during vehicle-mounted terminal operation, ensures the normal operation of the vehicle-mounted terminal, and expands various detection mechanisms on the basis of the traditional MCU reset circuit, so that it can be applicable to situations where the external conditions of the vehicle-mounted terminal are changeable, ensuring that the vehicle-mounted terminal can operate stably during its life cycle; among them, the power-on reset shutdown circuit can prevent the MCU from being unable to feed the dog during flashing, resulting in continuous reset and causing MCU flashing abnormalities; the low-voltage detection circuit can detect abnormal power loss of the car battery and feed back to the MCU. When the MCU detects that the battery is powered off, it enters the sleep mode in time to avoid sleep abnormalities after power loss; the ACC detection circuit can turn off the watchdog when ACC is OFF, to prevent the MCU in the sleep state from being reset by the watchdog. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural block diagram of the vehicle terminal MCU reset management circuit according to an embodiment of the present invention;

[0022] Figure 2 This is a circuit diagram of the vehicle terminal MCU reset management circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that an article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such article or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the article or device comprising the element.

[0025] In the description of the present invention, it should be noted that the terms "first", "second" and "third" are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "sleeved / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] See also Figure 1 and Figure 2 As shown, a vehicle terminal MCU reset management circuit includes:

[0028] The watchdog circuit 10 includes a watchdog chip U1;

[0029] Power-on reset shutdown circuit 11, and the reset pin of the watchdog chip U1 and the MCU, respectively, including a delay switch and a first switch tube Q1; when the battery is powered on, the delay switch controls the first switch tube Q1 connected to the reset pin to be turned off, and the end of the first switch tube Q1 connected to the MCU is in a high-impedance state; after a certain period of time, the delay switch controls the first switch tube Q1 to be turned on, and the reset pin of the watchdog chip U1 is electrically connected to the MCU;

[0030] Low voltage detection circuit 12, and the power monitoring input pin PFI and power monitoring output pin of watchdog chip U1 The power monitoring input pin PFI is connected to the battery power POW_IN, and the power monitoring output pin is connected to the MCU. When the MCU detects that the power monitoring output pin outputs a low level, it enters sleep mode.

[0031] The ACC detection circuit 13 is connected to the watchdog signal input pin WDI of the watchdog chip U1 to reset the MCU when the terminal device is abnormal.

[0032] In this embodiment, the delay switch includes a first resistor R1 and a first capacitor C1; one end of the first resistor R1 is connected to the MCU power supply DVDD_MCU, the other end of the first resistor R1 is connected to one end of the first capacitor C1 and the control end of the first switch tube Q1, and the other end of the first capacitor C1 is grounded; the input end of the first switch tube Q1 is connected to the reset pin of the watchdog chip U1, and the output end of the first switch tube Q1 is connected to the MCU.

[0033] The power-on reset shutdown circuit 11 further includes a first diode D1 ; the first diode D1 is connected in parallel with the first resistor R1 , and the anode of the first diode D1 is connected to the first capacitor C1 , and the cathode of the first diode D1 is connected to the MCU power supply.

[0034] The first switch tube Q1 is a triode; the control end of the first switch tube Q1 is the base, the input end of the first switch tube Q1 is the emitter, and the output end of the first switch tube Q1 is the collector.

[0035] When the traditional reset circuit is powered on, the 7th pin of the watchdog chip U1 Outputting a low level will reset the MCU. At this time, the MCU startup time cannot meet the startup time required by the car manufacturer. The present invention adds a power-on reset shutdown circuit 11 on the basis of the traditional watchdog. The power-on reset shutdown circuit 11 includes a first diode D1, a first resistor R1, a first capacitor C1, a first switch tube Q1 and a second resistor R2. When the vehicle terminal is started, the first resistor R1 and the first capacitor C1 form a delay switch. When the battery is powered on, the first capacitor C1 is charged, the base of the first switch tube Q1 is at a low level, and the first switch tube Q1 is in the cut-off state. The signal is in a high-impedance state, and the MCU starts normally by relying on its built-in power-on reset function. After time t (t=R1C1), the voltage level of the first capacitor C1 reaches the turn-on voltage of the base of the first switch Q1, the first switch Q1 is turned on, and the watchdog circuit 10 takes over monitoring.

[0036] In this embodiment, the low voltage detection circuit 12 includes a fifth resistor R5, a sixth resistor R6 and an eighth resistor R8; the battery power supply is connected to the power monitoring input pin PFI through the fifth resistor R5; the battery power supply is connected to the power monitoring output pin and the MCU respectively through the fifth resistor R5 and the sixth resistor R6 connected in series; one end of the eighth resistor R8 is connected between the fifth resistor R5 and the sixth resistor R6, and the other end of the eighth resistor R8 is grounded.

[0037] The low voltage detection circuit 12 also includes a seventh resistor R7 and a second switch tube Q2; the control end of the second switch tube Q2 is connected to the power detection adapter enable end to detect battery power supplies of different voltage systems, and the output end of the second switch tube Q2 is connected between the fifth resistor R5 and the sixth resistor R6 through the seventh resistor R7.

[0038] The low voltage detection circuit 12 further includes a second voltage regulator tube D2; the second voltage regulator tube D2 is connected in parallel with the eighth resistor R8, and the cathode of the second voltage regulator tube D2 is connected between the fifth resistor R5 and the sixth resistor R6, and the anode of the second voltage regulator tube D2 is grounded.

[0039] The second switch tube Q2 is a triode; the control end of the second switch tube Q2 is the base, and the output end of the second switch tube Q2 is the collector.

[0040] Depend on Figure 1As can be seen from the above, the low voltage detection circuit 12 is composed of the signals POW_IN, POWE_DET, POW_DET_EN, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the eleventh resistor R11, the twelfth resistor R12, the second voltage regulator D2, and the second switch Q2. The battery input signal POW_IN selects the surge-free signal after the front end of the vehicle terminal has been EMC processed and is connected to the 4-pin PFI of the watchdog chip U1. The watchdog chip U1 has a built-in comparator, which is referenced by the threshold U ref The voltage is 1.25V, when U gate When it is lower than Uref, POW_DET connected to the 5th pin PFO of the watchdog chip U1 outputs a low level. When the MCU detects that POW_DET is low, it enters sleep mode and saves key data.

[0041] The low voltage detection circuit 12 of this embodiment has a hysteresis function, which is mainly used to prevent the battery voltage (U POW_IN ) rebounds and causes the MCU to restart and shut down in an infinite loop. In the initial judgment, when Ugate = V low Less than or equal to U ref When U1 pin 5 outputs low level, MCU enters sleep mode. POW_IN When the voltage rises, U gate =V up Greater than V ref , the 5th pin of U1 outputs a high level and the MCU resumes startup.

[0042] At the same time, in order to adapt to the 12V system and 24V system commonly used in current automobiles, this embodiment sets POW_DET_EN as the power detection adaptation enable terminal of different voltage systems to ensure that the device performs low voltage power failure detection in 12V and 24V voltage systems. When POW_DET_IN is low, the second switch tube Q2 is turned off, and U gate The voltage of Ugate is determined by the fifth resistor R5, the sixth resistor R6 and the eighth resistor R8. At this time, the circuit is adapted to the 12V car system. When POW_DET_EN is set high, Q2 is turned on. At this time, the Ugate voltage is determined by the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8. At this time, the circuit is adapted to the 24V car system. The second voltage regulator D2 is used to ensure that Ugate is gate The voltage does not exceed the pin voltage limit of the watchdog chip U1 to prevent U1 from burning due to external surges.

[0043] V of 12V power supply system and 24V power supply system low and V up The calculation is as follows.

[0044] 12V system:

[0045]

[0046]

[0047] 24V system:

[0048]

[0049]

[0050] In this embodiment, the ACC detection circuit 13 includes a third switch tube Q3; the control end of the third switch tube Q3 is connected to the battery ignition signal, and the output end of the third switch tube Q3 is connected between the MCU power supply and the dog feeding signal input pin of the watchdog chip U1; the dog feeding signal input pin is also connected to the MCU; when the battery ignition signal is invalid, the third switch tube Q3 is controlled to be cut off, the dog feeding signal input pin of the watchdog chip U1 is in a high-impedance state, and the watchdog chip U1 stops working; when the battery ignition signal is valid, the third switch tube Q3 is controlled to be turned on, the dog feeding signal input pin of the watchdog chip U1 is connected to the MCU, and the watchdog chip U1 keeps working.

[0051] The third switch tube Q3 is a triode; the control end of the third switch tube Q3 is the base, and the output end of the third switch tube Q3 is the collector.

[0052] The watchdog chip U1 of this embodiment can be a conventional watchdog IC. When WDI is continuously high or low for more than 1.6 seconds, the watchdog timer overflows and the ACC detection circuit 13 outputs a reset signal. Conversely, when WDI has a high-low transition signal within 1.6 seconds, the watchdog timer is reset, the ACC detection circuit 13 does not output a reset signal, and the MCU maintains normal operation.

[0053] from Figure 1 As can be seen, the ACC detection circuit 13 also includes a tenth resistor R10, a third diode D3, a thirteenth resistor R13, and a fourteenth resistor R14. It should be noted that the ACC detection circuit 13 can be implemented in multiple ways; this embodiment only illustrates one reverse detection circuit. Specifically, when the battery ignition signal ACC_IN is invalid, ACC_IN is low, nACC_DET is high, the MCU's WDI output signal is set to high impedance, and the watchdog timer stops operating. When ACC_IN is valid, ACC_IN is high, nACC_DET is low, and the watchdog timer remains operational regardless of the WDI state.

[0054] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A vehicle terminal MCU reset management circuit, characterized in that: include: A watchdog circuit, including a watchdog chip; The power-on reset shutdown circuit is connected to the reset pin of the watchdog chip and the MCU respectively, and includes a delay switch and a first switch tube. When the battery is powered on, the delay switch controls the first switch tube connected to the reset pin to be turned off, and the end of the first switch tube connected to the MCU is in a high-impedance state. After a certain period of time, the delay switch controls the first switch tube to be turned on, and the reset pin of the watchdog chip is electrically connected to the MCU. The low-voltage detection circuit is connected to the power monitoring input pin and the power monitoring output pin of the watchdog chip respectively; the power monitoring input pin is connected to the battery power supply, and the power monitoring output pin is connected to the MCU. When the MCU detects that the power monitoring output pin outputs a low level, it enters sleep mode; The ACC detection circuit is connected to the dog feeding signal input pin of the watchdog chip. When ACC is OFF, the watchdog can be turned off to prevent the MCU in sleep state from being reset by the watchdog.

2. The vehicle-mounted terminal MCU reset management circuit according to claim 1, characterized in that: The delay switch includes a first resistor and a first capacitor; one end of the first resistor is connected to the MCU power supply, the other end of the first resistor is connected to one end of the first capacitor and the control end of the first switch tube, and the other end of the first capacitor is grounded; the input end of the first switch tube is connected to the reset pin of the watchdog chip, and the output end of the first switch tube is connected to the MCU.

3. The vehicle-mounted terminal MCU reset management circuit according to claim 2, characterized in that: The power-on reset shutdown circuit also includes a first diode; the first diode is connected in parallel with the first resistor, and the anode of the first diode is connected to the first capacitor, and the cathode of the first diode is connected to the MCU power supply.

4. The vehicle terminal MCU reset management circuit according to claim 2, characterized in that: The first switch tube is a triode; the control end of the first switch tube is the base, the input end of the first switch tube is the emitter, and the output end of the first switch tube is the collector.

5. The vehicle-mounted terminal MCU reset management circuit according to claim 1, characterized in that: The low-voltage detection circuit includes a fifth resistor, a sixth resistor and an eighth resistor; the battery power supply is connected to the power monitoring input pin through the fifth resistor; the battery power supply is connected to the power monitoring output pin and the MCU respectively through the fifth resistor and the sixth resistor connected in series; one end of the eighth resistor is connected between the fifth resistor and the sixth resistor, and the other end of the eighth resistor is grounded.

6. The vehicle terminal MCU reset management circuit according to claim 5, characterized in that: The low-voltage detection circuit also includes a seventh resistor and a second switch tube; the control end of the second switch tube is connected to the power detection adapter enable end to detect battery power supplies of different voltage systems, and the output end of the second switch tube is connected between the fifth resistor and the sixth resistor through the seventh resistor.

7. The vehicle-mounted terminal MCU reset management circuit according to claim 5, characterized in that: The low voltage detection circuit also includes a second voltage regulator tube; the second voltage regulator tube is connected in parallel with the eighth resistor, and the cathode of the second voltage regulator tube is connected between the fifth resistor and the sixth resistor, and the anode of the second voltage regulator tube is grounded.

8. The vehicle terminal MCU reset management circuit according to claim 5, characterized in that: The second switch tube is a triode; the control end of the second switch tube is the base, and the output end of the second switch tube is the collector.

9. The vehicle-mounted terminal MCU reset management circuit according to claim 1, characterized in that: The ACC detection circuit includes a third switch tube; the control end of the third switch tube is connected to the battery ignition signal, and the output end of the third switch tube is connected between the MCU power supply and the watchdog chip's dog feeding signal input pin; the dog feeding signal input pin is also connected to the MCU.

10. The vehicle terminal MCU reset management circuit according to claim 9, characterized in that: The third switch tube is a triode; the control end of the third switch tube is the base, and the output end of the third switch tube is the collector.

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